D1.L.3.2.3 Compression
The allowable compressive stress for columns, except those fabricated from austenitic stainless steel shall be as required by NF-3322.1(c)(1). The allowable compressive stress for columns fabricated from austenitic stainless steel shall be as required by NF-3322.1(c)(2). The allowable compressive stress for member elements other than columns constructed by any material, including austenitic stainless steel, shall be as required by NF-3322.1(c)(3).
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Gross Sections of Columns, except those fabricated of austenitic stainless steel:
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On gross section of axially loaded compression members, when (Kl/r) < Cc ,
Where:
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When (Kl/r) > Cc ,
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When (Kl/r) > 120,
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Gross sections of columns fabricated from Austenitic Stainless steel:
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When (Kl/r) ≤ 120,
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When (Kl/r) > 120,
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Member elements other than columns:
- For Plate Girder Stiffeners, Fa = 0.60·Fy
- For webs of rolled shapes, Fa = 0.75·Fy
The above clauses are applicable only when the width-thickness ratio of the element satisfies all the sub-sections of NF-3322.2(d).
If the above-mentioned clauses are not satisfied,
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For un-stiffened compression element, a reduction factor, Qs, is introduced. Detailed values of Qs for different shapes are given in NF-3322.2(e)(2)(a) to NF-3322.2(e)(2)(d).
In the case for angles or plates projecting from compression members and for projecting elements of compression flanges of girder,
When ,
When ,
Where:
- when h/t > 70, otherwise, kc = 1.0.
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For stiffened compression element, a reduced effective width, be, is introduced.
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For the flanges of square and rectangular sections of uniform thickness:
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For other uniformly compressed elements:
Consequently, a reduction factor, Qa, equal to the effective area divided by the actual area is introduced.
Combining both these factors, allowable stress for axially loaded compression members containing stiffened or un-stiffened elements shall not exceed
Where:
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